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One second PAUSE in 18 Stage LED Sequencer?

I was looking at Bill Bowden's 18 Stage LED Sequencer circuit at:

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(using cascaded 4017 decade counters) and I had a question about its operation - actually, about the SMOOTHNESS of its operation.

It looks like we would have a smooth blink rate from LED 1 through LED

9, a pause during second #10, then, starting at second #11, LEDs 10 through 18 would light up.

Is that correct or am I looking at this wrong?

I was trying to find a circuit that would give me:

  1. A smooth 16 LED sequence blink rate,
  2. For one 16 LED one-way sequence,
  3. And then STOP after the 16th LED was done.

Will Bill Bowden' s circuit do that - or does anyone know a better circuit?

Thanks,

Keith

Reply to
locator299
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There is indeed a very small pause during second 10, but it is (way) less than a microsec (I haven't looked up the 4017 datasheet). The main clock advances the right counter which activates pin 11. When this pin goes high it enables the clock for the left counter. If at this moment the clock is still active (high) the left counter will (almost) immediately see a rising edge on its clock input and advance one step. So there will be no visible pause if the clock high-time is a bit longer than the propagation delay of the right counter (from clock to pin 11). In Bill Bowden's circuit this condition is largely met.

For your application you could use pin 9 of the left counter to block the clock by connecting it through a diode to pin 2 of the 555 (anode to pin 9). This will stop the oscillator. To get things going again you could toggle the power or add a reset switch (4017 pins 15 to gnd).

--DF

Reply to
Deefoo 

--
Do you want the 16th LED to stay on at the end of the sequence or to
go off?
Reply to
John Fields

The OP said "STOP after the 16th LED was done" so I suppose this means off.

--DF

Reply to
Deefoo 

--
Yes, but rather than suppose, I\'d like to know for sure.
Reply to
John Fields

Thank you for your help. Yes, I wanted to press a button to start the sequence, have LEDs 1 thru 16 light up (in sequence) and then STOP the sequence automatically after the 16th LED has lit up.

locator299

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Reply to
locator299 

--
That was over three years ago!

Do you still want a circuit?

JF
Reply to
John Fields

locator299

------------------------------------- John Fields wrote:

No, after reading Deefoo's comments, I was able to finish the circuit. I used Deefoo's suggestions to stop the sequence early and to reset the circuit. Thank you, Deefoo! I'm sorry that it took me so long to get back. Fate had me pretty busy on other projects for a while, but now I'm back to pick up where I left off. Again, thank you for your help!

locator299

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Reply to
locator299

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